FIG. 7 shows a schematic exploded view of a conventional batting practice apparatus, including an installation hole 61 on a base plate 60, and a ball holder 62 engaged to base plate 60 via a connecting set. The connecting set includes a first connecting element 63, a second connecting element 64 and a locking element 65. For assembly, first connecting element 63 partially extends through installation hole 61 to the top surface of base plate 60, second connecting element 64 is screwed tightly to the segment of first connecting element 63 extending above base plate 60, and then ball holder 62 is inserted to second connecting element 64. Finally, locking element 65 is crewed tightly to second connecting element 64. In this manner, ball holder 62 is foxed to base plate 60. However, the above structure has the following disadvantages:                1. The ball holder requires a connecting set having a plurality of connecting elements to engage to the base plate. The assembly and the disassembly are both inconvenient. In addition, the more elements the structure has, the higher the manufacturing cost is.        2. The batting practice apparatus using the conventional structure only has the top segment close to the tip of the ball holder made of resilient rubber material to annihilate the force acted on the ball holder during batting practice. However, the strength of the above structure is insufficient, and therefore, a heavy weight object is usually added to the base plate to using nails to temporarily fix the base plate to the ground during batting practice to prevent the batting practice apparatus from tipping over.        
Therefore, it is imperative to devise a ball holder and base fix structure of batting practice apparatus to overcome the disadvantages in the conventional structures.